1. Field of the Invention
The present invention relates to a motorized rocking machine for imparting reciprocal, oscillating motion to a hammock; and more particularly, to motorized hammock rocker that automatically sustains the rocking motion of an occupant recumbent on a conventional hammock.
2. Description of the Prior Art
A variety of rockers have been contemplated in the art, enabling oscillating movement of baby carriages, swings, hammocks and the like. These devices include for example, electrical motor driven devices and energy storage devices having spring wound drivers. Oftentimes such prior art devices have too little energy available to sustain the rocking motion, thereby causing the rocker to exhibit movement that is inconsistent with the desired rocking motion of the user. Many of the devices require some form of initiation and do not provide rocking movement automatically when the user climbs onto the hammock.
U.S. Pat. No. 657,893 to Lowe discloses a home hammock motor. This hammock motor is a spring-wound device. It requires an initial push to actuate the rocking motion. The device does not start automatically; but needs an initial push from an attendant.
U.S. Pat. No. 669,980 to Cutten discloses a hammock swinger. This hammock swinger is attached to the ground, and has an arm connected to the hammock by a rope or cable. The arm movement is made possible by a wound up, strong spring. A trip mechanism changes the direction of movement of the arm when the swinging limit of the hammock applies tension to the trip mechanism. During the time that the arm is powering the rocking motion of the hammock, the cable is in tension. When the hammock reaches its rocking limit, the tension is suddenly released. A trip mechanism is thereby activated, and rocking discontinues. Propulsion of the rocker is effected by a strong spring. The '980 patent contains no disclosure concerning the spring winding mechanism.
U.S. Pat. Nos. 751,125 and 812,387 to Wertz et al. disclose a swinging hammock. This swinging hammock is propelled by a spring-powered device that is hinged on a rod proximate to the hammock. The spring-powered device is suspended from a bar which carries the hammock. The spring-powered device is key-wound, and clock-like, having a main spring, a ratchet and pawl, one or more wheels and a pallet wire. An escapement releases the spring's energy to the rocking movement. It is controlled by a release bar, which is maintained plumb by the weight of a person using the hammock. The small spring likely has insufficient energy to rock a hammock when weighted by an occupant.
U.S. Pat. No. 1,420,134 to Nisle discloses a cradle. A rocking motion is imparted to the cradle by a geared down electric motor, which is placed on the base that drives an eccentric connecting rod. The connecting rod imparts oscillating motion to the cradle. A relatively large electric motor is required to provide adequate torque when geared down to rock the cradle and its occupant. Power requirements for the system make it unlikely that rocking motion would be imparted to a hammock when the occupant is an adult.
U.S. Pat. No. 1,505,117 to Withun discloses an electrically operated swing. The rotational speed of the electric motor is first decreased by gearing and is again reduced by a worm gear to rotate a disk. The disk drives an eccentric actuation rod, which pulls on an oscillating lever to rock the cradle. The geared motor must supply high torque to impart all the rocking movement. There is no matching between the harmonic character of swing oscillations and the rotational speed of the disk. The cradle and its occupant are much lighter than a hammock that is occupied by an adult.
U.S. Pat. No. 1,727,635 to Crane discloses an automatic swinging crib. The automatic swinging crib is provided with a solenoid. It is energized by a contact attached to the frame during a portion of the swing cycle, which draws current from a battery. The contact is broken de-energizing the solenoid when the armature reaches the mid point of the solenoid. Energy is thereby provided to the swinging crib at a portion of the swing cycle to combat slowing down of the swing motion. No motors are utilized by the system. The partial cycle solenoid energization is too weak to swing other than small objects, such as a baby. The swinging device disclosed by the '635 patent disclosure is incapable of rocking a hammock occupied by an adult.
U.S. Pat. No. 2,793,375 to Wardell Jr. discloses self-rocking hammock. The hammock is rocked manually by the hammock occupant. Rocking is accomplished, using a foot pedal. No electrical motor is extant in this device. The hammock does not automatically rock when the user climbs onto it. Construction of the hammock is non-standard; the hammock is suspended between rails attached to a semi-circular frame.
U.S. Pat. No. 3,453,999 to Neal discloses an apparatus and process for rocking an infant. A compound-motion infant hammock is placed in an incubator to stimulate the infant's vestibular apparatus. The motor drive oscillates the hammock in the horizontal plane by about 120 degrees, while it rocks the hammock in the vertical plane by about 30 degrees. Rocking of the hammock is atypical. The compound motion generated by the motor drive provides unexpected movement that is unsuited for a conventional hammock.
U.S. Pat. No. 3,842,450 to Pad discloses oscillating furniture and playthings. The oscillating furniture or plaything can comprise a cradle, rocking chair, swinging garden seat, hammock, swing or rocking horse. An electromagnetic oscillation device has a ferromagnetic core movable axially relative to a hollow coil support of an electromagnet. A switch is arranged so that after a given change in the direction of oscillation of the furniture, a circuit is closed to intermittently supply current to the electromagnet and provide oscillation maintaining impulses. There is no electrical motor in this device. A stationary electromagnetic device with a slidable ferromagnetic core is pulled by a hollow electromagnetic coil when energized. The coil is energized intermittently by a switch connected to power supply at a certain portion of the oscillation cycle. This electromagnetic device only sustains the oscillation by supplying a small amount of power during a portion of the oscillation cycle. It cannot initiate an oscillation. For this reason, the oscillating furniture has to be pushed first. If the switch is turned on initially due to the position of the cradle, it is possible to supply uninterrupted power to the coil. The movable ferromagnet becomes stuck within the coil, making it impossible to start the oscillation. The coil is likely burn out due to prolonged passage of current.
U.S. Pat. No. 4,491,317 to Bansal discloses an electrically powered swing for an infant. Swing oscillation is maintained by an intermittently powered solenoid activated by a microswitch tripped by the swinging motion. There is no electrical motor in this device. Closure of the microswitch draws power from a battery in the form of short DC pulses providing power to maintain swinging movement of the infant swing. In order for the solenoid to provide power that maintains the oscillation, the device must first be swung manually. Due to the intermittent nature of energization by the solenoid, only an infant swing may be sustained. Energy mustered by the device is sufficient merely to maintain swings carrying infants. The device has insufficient power to be used on a conventional hammock occupied by an adult.
U.S. Pat. No. 4,911,429 to Ogbu discloses a motorized swing. The swing is attached to a rod, which is mounted on two bases with vertical posts. The rod has two motor drives with L shaped downward facing pivot control arms, and control cables are attached to the infant seat. The relative orientation of these two L shaped pivotal control arms determines whether the infant seat is wobbled or swayed. The device imparts a wobbling or swaying motion to the infant seat. It is unsuited for rocking a hammock occupied by an adult. Multiple control cables effect wobbling or swaying motion to the infant seat. These cables cannot be easily attached to a conventional hammock, which is generally suspended from two fixed locations.
U.S. Pat. No. 4,987,624 to Nafti discloses a device for imparting multi-directional rocking motion. The device is attached to child seat, cradle or rocking horse, using a spring loaded attachment clamp. The motor contained within the housing moves the reciprocating arm, which rests on a stationary surface such as a floor, providing a rocking motion. This device only moves objects up and down; it does not result in a rocking movement. Therefore, this device is unsuited to create rocking motion for a conventional hammock. The rocking motion is not initiated when a person uses the attached device. Accordingly, the movement does not begin when a person climbs onto the hammock.
U.S. Pat. No. 5,139,462 to Gabe discloses an automated swing. This automated swing includes a support frame assembly and a swinging frame assembly pivotally mounted to the support frame assembly. The swing has a pair of parallel elliptical pulleys mounted on a drive shaft driven by a motor drive. A resilient flexible belt is wrapped around the elliptical pulleys and a bearing, and attached to the infant seat suspended on a bar. The elliptical pulleys apply increased tension in one side or other of the belt providing swinging movement. This drive system is suited for swinging an infant seat. The rubber bands are generally not strong and elliptical pulleys only generate limited tension in the resilient belts. Besides, the belts need to be attached to a solid body such as an infant's chair to take advantage of the tension to drive the seat into swinging motion. A conventional hammock is flexible and is not solid. Therefore, a belt tensioned by an elliptical pulley cannot be used to rock a hammock. The elliptical pulleys are on a separate drive shaft and this cannot be provided for a hammock attached between two fixed supports.
U.S. Pat. No. 5,574,339 to Kattwinkel et al. discloses a drive for rocking furniture. A piece of furniture has a frame and a part capable of rocking on the frame at a natural rocking frequency. A drive has a sensor for detecting movement of the part on the frame. A drive motor is connected between the frame and the part for rocking the part on the frame. The sensor detects angular movement, that is, angular speed, angular position, and/or angular acceleration of the part on the frame. A controller is connected between the drive and sensor for rocking the part on the frame at its natural rocking frequency up to a predetermined maximum angular displacement of the part on the frame. The controller has a response field and operates the drive within the specified angular displacement using fuzzy logic. The amount of energy needed to maintain the oscillation is minimal at the eigenfrequency or natural frequency; it is merely enough to overcome frictional and other losses. Limiting the maximum angular travel is easily accomplished regardless of the motor characteristic curve and other parameters. This system uses a fuzzy logic controller that uses response of angular velocity, angular acceleration from a moving part in the rocking moving part to first determine the natural frequency of the part and strive to drive the motor at the natural frequency. At resonance, the energy needed to maintain rocking movement is minimal, but the amplitude of oscillations can build very rapidly unless damping within the system exists. However, the disclosure states that the angular displacement is maintained within the maximum limit. How this objective is achieved is unclear, since at resonance the maximum limit for angular displacement can be easily exceeded.
U.S. Pat. Nos. 6,254,490 and 6,361,446 to Lawson et al. disclose an automated swinging device. This automatic swing device is used in combination with a conventional porch swing. It includes a frame member that will support a conventional porch swing. An automatic swinging device has a fractional horse power motor that runs all the time and uses a clutch to initiate swinging power. An initiation assembly is coupled to the rotating arm assembly. This initiation assembly includes a clutch arm that is connected to a stop unit. The stop unit is connected to the fractional horsepower gear motor. In operation, the user sits on the swing and pushes back, this will cause the rotating arm assembly and active the initiation assembly, disengaging the stop unit. The automatic swinging device is connected to a swing, not a hammock. It does not start swinging as soon as the user gets on the swing. The user has to push back to activate the initiation assembly. The motor is not turned on when the user gets on the swing. It runs all the time. Due to mechanical complexities of this device it is usable with a conventional porch swing, but is not usable with a conventional hammock that is attached to two fixed locations.
Notwithstanding the efforts of prior art workers to provide automatic swinging attachments to a conventional hammock, there is a need for a simple to operate, automatic swinging device attached to a hammock that senses when a user climbs onto a hammock and rocks at a comfortable frequency that is varied in accordance with the weight of the user and an initial movement that is selected by the user.